The objective of the research is to define the functional interrelationships between those neuronal types which comprise central networks which govern the discharges of sympathetic nerves which subserve cardiovascular function. Three major problems are under investigation. 1. Organization of brain stem and hypothalamic circuits involved in generating sympathetic nerve discharge. 2. Organization of baroreceptor reflex circuits. 3. Organization of spinal sympathetic circuits. The experimental animal is the cat. Computer-aided analysis is used to examine the relationships between the activity of single brain stem and spinal neurons and that of populations of pre- and postganglionic sympathetic nerve fibers.